One major issue concerning investigations of visual perception is determination of the geometrical properties of visual space. To address this issue, one must determine the relationships between geometrical features of visual space, distance, direction, angle, and size. Consistent evidence indicates that visual angle is a determinant of perceived exocentric distance. Previous evidence suggests that exocentric distance and direction are hierarchically processed, with distance preceding direction. The present study investigated the relationship between the perceptual processing of egocentric direction and exocentric direction using a task that independently provides both perceptual variables in a single judgment. The results indicated that egocentric directions were systematically overestimated, and this was not caused by either the global shape of the layout or leg length effects. Exocentric directions presented a discontinuous pattern of overestimation of smaller angles that were subtended by radial orientations and accuracy of right angles that were subtended by horizontal orientations. This could be explained by the anisotropy of visual space, a well-established phenomenon from visual space studies. The analysis of the association between the processing of these two variables revealed independence between them in which exocentric direction processing did not depend on the processing of egocentric direction processing, and vice versa. The present results and prior evidence converge on the notion of hierarchical processing in which the visual system processes the egocentric distance of objects followed by exocentric distance processing and subsequent processing. The precise positions of egocentric and exocentric directions in this chain of processing remain to be determined.

Os indícios binoculares foram considerados a informação prevalente na determinação da profundidade desde os primórdios da pesquisa em visão. No presente estudo, duas respostas perceptivas, o clássico relato verbal e um método mais recente, o caminhar em ciclo aberto, foram empregados para verificar o papel da informação binocular na percepção de distâncias egocêntricas. Em duas condições de indícios, plena e reduzida de indícios visuais, os observadores julgaram e caminharam distâncias egocêntricas de estímulos apresentados no nível do olho, sob visão binocular ou monocular. Os resultados indicaram constância perceptual para caminhar em ciclo aberto e respostas sob visão binocular, assim como baixa performance sob forte degradação da informação visual (condição reduzida de indícios sob visão monocular), nos fornecendo subsídios para sustentar o papel fundamental da informação binocular na percepção de distâncias egocêntricas. Além disso, as ações visualmente dirigidas podem ser medidas adequadas da distância percebida, com fidedignidade maior que o relato verbal, já que é relativamente incólume à intrusão de processos inferenciais e tendências perceptuais. Somando-se a isso, reduzidos movimentos da cabeça, tanto translacionais quanto deflexões para frente e para trás, podem ter contribuído para uma quase perfeita interação entre a disparidade binocular e as respostas de caminhar em ciclo aberto.

Binocular cues were considered the prevailing information on specifying depth since the beginning of vision research. In the present study, two perceptual responses, the classical verbal report and a more recent method, open-loop walking, were used to assess the role of binocular information for egocentric distance perception. In two cue conditions environments, full- and reduced-cue, observers judged and walked egocentric distances of stimuli presented at eye-level, under binocular or monocular viewing. Results indicated perceptual constancy for open-loop walking and binocular responses, as well as poor performances under strong degradation on visual information (reduced-cue under monocular viewing), thus presenting evidence to support the fundamental role of binocular information on perception of egocentric distances. Besides that, visually directed actions could be adequate measures of perceived distance, with a better reliability than verbal report, since they were quite free of intrusion of inferential processes and perceptual tendencies. In addition, reduced head movements, side-to-side as well as back and forth deflexion movements, could have contributed to a near perfect coupling between binocular disparity information and open-loop walking responses.